Lighting reproduction typically involves using computer-controlled light sources to illuminate a real-world subject as it would appear within a particular real-world environment. The light sources, which may be aimed toward the subject from many directions, can be driven to various intensities and colors to best approximate the illumination within the real-world environment. One application for this technique is to realistically composite the subject into a scene, for example to composite an actor in a studio into a faraway location such as a cathedral. When the actor is illuminated by a close approximation of the lighting originally present in the cathedral, then such a composite may believably show the actor standing within the cathedral.
One challenge in lighting reproduction is that real-world illumination and subjects tend to have complex spectral properties, because lighting and reflectance are functions of wavelength across the visible spectrum, often with significant variations. In contrast, the light sources in lighting reproduction systems typically use only three channels of illumination color, i.e. the conventional red, green, and blue (RGB) channels, which can be produced by appropriately colored LEDs (light emitting diodes). Although RGB colors are commonly used in computer graphics, it may be difficult to accurately compute the color of light reflecting from a surface of a subject without knowing the spectrum of the illuminant and the spectral reflectance of the subject surface. When the illuminant spectrum and the spectral reflectance of the subject surface are not taken into account, it may be hard to accurately reproduce the subject's appearance under complex real-world illumination spectra such as tungsten and fluorescent lighting using just RGB lights.
Accordingly, there is a need for improved color matching techniques in lighting reproduction systems.